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Search Results: 1 - 10 of 11062 matches for " Alexandre Christófaro;Pessenda "
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Pedological and isotopic relations of a highland tropical peatland, Mountain Range of the Espinha?o Meridional (Brazil)
Horák, Ingrid;Vidal-Torrado, Pablo;Silva, Alexandre Christófaro;Pessenda, Luiz Carlos Ruiz;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000100004
Abstract: the evolution of organic matter sources in soil is related to climate and vegetation dynamics in the past recorded in paleoenvironmental quaternary deposits such as peatlands. for this reason, a histosol of the mineralotrophic peatland from the pau-de-fruta special protection area - spa, espinha?o meridional, state of minas gerais, was described and characterized to evidence the soil constituent materials and properties as related to changes in environmental conditions, supported by the isotopic and elementary characterization of soil c and n and 14c ages. samples were collected in a depression at 1,350 m asl, where histosols are possibly more developed due to the great thickness (505 cm). nowadays, the area is colonized by vegetation physiognomies of the cerrado biome, mainly rocky and wet fields (campo rupestre and campo úmido), aside from fragments of semidecidual seasonal forest, called cap?es forests. the results this study showed that early the genesis of the analyzed soil profile showed a high initial contribution of mostly herbaceous organic matter before 8,090 ± 30 years bp (14c age). in the lower-mid holocene, between 8,090 ± 30 years ap (14c age) to ± 4,100 years bp (interpolated age), the vegetation gradually became more woody, with forest expansion, possibly due to increased humidity, suggesting the existence of a more woody cerrado in the past than at present. drier climate conditions than the current were concluded ± 2,500 years bp (interpolated age) and that after 430 years bp (14c age) the forest gave way to grassland, predominantly. after the dry season, humidity increased to the current conditions. due to these climate fluctuations during the holocene, three decomposition stages of organic matter were observed in the histosols of this study, with prevalence of the most advanced (sapric), typical of a deposit in a highly advanced stage of pedogenetic evolution.
Genesis and classification of Oxisols in a highland toposequence of the upper Jequitinhonha Valley (MG)
Ferreira, Celmo Aparecido;Silva, Alexandre Christófaro;Torrado, Pablo Vidal;Rocha, Welington Willian;
Revista Brasileira de Ciência do Solo , 2010, DOI: 10.1590/S0100-06832010000100020
Abstract: the brazilian system of soil classification (sibcs) is a taxonomic system, open and in permanent construction, as new knowledge on brazilian soils is obtained. the objective of this study was to characterize the chemical, physical, morphological, micro-morphological and mineralogical properties of four pedons of oxisols in a highland toposequence in the upper jequitinhonha valley, emphasizing aspects of their genesis, classification and landscape development. the pedons occupy the following slope positions: summit - red oxisol (lv), mid slope (upper third) - yellow-red oxisol (lva), lower slope (middle third)- yellow oxisol (la) and bottom of the valley (lowest third) - "gray oxisol" ("lac"). these pedons were described and sampled for characterization in chemical and physical routine analyses. the total fe, al and mn contents were determined by sulfuric attack and the fe, al and mn oxides in dithionite-citrate-bicarbonate and oxalate extraction. the mineralogy of silicate clays was identified by x ray diffraction and the fe oxides were detected by differential x ray diffraction. total ti, ga and zr contents were determined by x ray fluorescence spectrometry. the "lac" is gray-colored and contains significant fragments of structure units in the form of a dense paste, characteristic of a gleysoil, in the horizons a and ba. all pedons are very clayey, dystrophic and have low contents of available p and a ph of around 5. the soil color was related to the fe oxide content, which decreased along the slope. the decrease of crystalline and low- crystalline fe along the slope confirmed the loss of fe from the "lac". total si increased along the slope and total al remained constant. the clay fraction in all pedons was dominated by kaolinite and gibbsite. hematite and goethite were identified in lv, low-intensity hematite and goethite in lva, goethite in la. in the "lac", no hematite peaks and goethite were detected by differential x ray diffraction. the micro-morphology indi
Doen as foliares da alfafa (Medicago sativa L.), em Lavras, Minas Gerais
Pereira Rosana Cristina,Evangelista Ant?nio Ricardo,Souza Paulo Estev?o de,Silva Alexandre Christófaro
Revista Brasileira de Zootecnia , 2003,
Abstract: Objetivou-se verificar as doen as foliares que ocorrem na alfafa em Lavras-MG, no período de setembro de 1997 a outubro de 1998. Um ensaio foi conduzido em blocos ao acaso em esquema de parcelas subdivididas. Nas parcelas foram alocadas foram 35 cultivares e nas subparcelas 11 épocas de avalia o. Avalia es foram realizadas aos 28 dias após corte, quando foram coletadas dez hastes de alfafa por parcela para avalia o da desfolha e determina o da severidade das doen as. Os dados foram submetidos à análise de variancia e os contrastes entre médias comparados pelo teste de Scott-Knott a 5%. A mancha-de-Leptosphaerulina ocorreu durante o ano todo, porém com maior severidade nos períodos mais frios do ano. A mancha-negra-das-folhas-e-caule apresentou maior severidade no final do ver o e início do outono e a ferrugem revelou maior severidade apenas nas avalia es de novembro. As maiores porcentagens de desfolha foram obtidas nos meses mais frios do ano. As cultivares mais resistentes à mancha-de-Leptosphaerulina, cercosporiose e à desfolha foram a Crioula, P30 e Costera SP INTA. As cultivares MH 15 e MH 4 destacaram-se pela maior resistência à ferrugem.
Gênese de solos derivados de rochas ultramáficas serpentinizadas no sudoeste de Minas Gerais
Vidal-Torrado, Pablo;Macias, Felipe;Calvo, Rosa;Carvalho, Sebasti?o Gomes de;Silva, Alexandre Christófaro;
Revista Brasileira de Ciência do Solo , 2006, DOI: 10.1590/S0100-06832006000300013
Abstract: soils formed from serpentinized rocks or serpentinites constitute a special group of soils on the earth surface. these rocks present ultramafic characteristics, with more than 70 % mafic minerals (iron and magnesium oxides). the mineralogy of serpentinites is poor in silica and aluminum and very rich in mg. only few studies have looked into the morphology, mineralogy, genesis and classification of soils developed on this type of parent material. in the humid-tropical climate of southwestern minas gerais state, three representative soil profiles were taken from the morro do ferro, in the greenstone belt area, on young geomorphic surfaces. they were characterized by macro and micromorphological descriptions, particle size distribution and chemical analysis, and x ray mineralogical analysis of the clay and sand fractions. the geochemical alterations in the soil horizons were characterized by edrx microanalyses of soil thin sections. the soils were classified as haplic phaeozern eutric regosol and chromic cambisol. although these soils are developed in a climate that favors quick weathering, from a morphological and mineralogical point of view they are similar to soils derived from serpentinized rocks in sub-tropical and temperate regions. the process of soil formation shows an evolution of the related distribution as follows: rock alteration ? fragmic related distribution ? vughy porphyric related distribution ? open porphyric related distribution due to vugh coalescence. argilluviation is evident and appears in two different phases: primary argilluviation that occurs between fissures and vughs formed by rock alteration and secondary argilluviation found in the more open and evolved coalesced vughs. the mineralogy of these soils is somewhat uncommon for tropical soils, with the presence of easily weatherable primary minerals in the clay fraction, especially talc, trioctahedral chlorite and, to a lesser extent, tremolite. the latter is abundant in the silt fraction. iro
Doen?as foliares da alfafa (Medicago sativa L.), em Lavras, Minas Gerais
Pereira, Rosana Cristina;Evangelista, Ant?nio Ricardo;Souza, Paulo Estev?o de;Silva, Alexandre Christófaro;Muniz, Joel Augusto;
Revista Brasileira de Zootecnia , 2003, DOI: 10.1590/S1516-35982003000600002
Abstract: it was aimed to verify the chief leaf diseases that occurs in alfalfa, in lavras-mg, state of minas gerais, of 1997 september to 1998 october. a randomized block trial subplots in time, whose factors were 35 alfalfa cultivars in the plots and 11 evaluation times, which corresponded to the months, in subplots. evaluations were performed at 28 days after the cut, when ten stems here collected by plots for evaluation of defoliation and determination of severity of the diseases. the data here submitted to the variance analysis and the contrasts among averages compared by scott-knott test at 5%. the leaf spot happened during the whole year, with a greatest severity in the periods more colds of the year. the summer black stem and leaf spot, it presented greater severity at the end of summer and beginning of the autumn and the rust reveled a greatest severity in the evaluations of november. the most resistant cultivars to leaf spot, summer black stem and leaf spot and defoliation were crioula, p 30 and costera sp inta. the cultivars mh 15 and mh 4 stood out by larger resistance to the rust.
Turfeiras da Serra do Espinha?o Meridional - MG: II - influência da drenagem na composi??o elementar e substancias húmicas
Silva, Alexandre Christófaro;Horák, Ingrid;Vidal-Torrado, Pablo;Cortizas, Antonio Martinez;Racedo, Jose Rodrigues;Campos, José Ricardo da Rocha;
Revista Brasileira de Ciência do Solo , 2009, DOI: 10.1590/S0100-06832009000500031
Abstract: peat bogs are organosols formed under ideal ecological conditions in terms of the accumulation of organic material, controlled by geomorphological and geological processes and climate. the physical, chemistry and biological constitution of peat bogs is largely unknown. in this study the peat bogs of the southern serra do espinha?o (minas gerais, brazil) were described and sampled from three profiles at 1,250 m (p1), 1,350 m (p4) and 1,800 m (p2) above sea level. the three profiles were characterized morphologically, the collected samples were chemically analyzed and the organic matter was fractioned in humin, fulvic and humic acids. the organic matter of the peat bog profiles differed strikingly in chemical composition and contents of humic substances and in the chemical composition of humic acids. the variations in drainage conditions were mostly responsible for the qualitative and quantitative differentiation of organic matter. in peat bog p1, with moderate drainage, the c/n and o/c ratios of the organic matter were higher, fulvic acid predominant among the humic substances and humic acids had a higher c/n ratio. in the peat bog p2 and p4, with very poor drainage, c/n and o/c ratios were lower in the organic matter, humin largely predominant among humic substances and c/n ratios in humic acids were lowest.
Turfeiras da Serra do Espinha?o Meridional - MG: I - caracteriza??o e classifica??o
Silva, Alexandre Christófaro;Horák, Ingrid;Cortizas, Antonio Martinez;Vidal-Torrado, Pablo;Racedo, Jose Rodrigues;Grazziotti, Paulo Henrique;Silva, Enilson de Barros;Ferreira, Celmo Aparecido;
Revista Brasileira de Ciência do Solo , 2009, DOI: 10.1590/S0100-06832009000500030
Abstract: peat bogs are a special environment for studies related with the dynamics of organic matter, landscape evolution and climatic changes and with local, regional and global cycles of atmospheric pollution. peat bogs contribute to the global c sequestration, act as water reservoirs and are the habitat of an endemic biodiversity. the serra do espinha?o meridional (minas gerais state, brazil) - sdem - a terrestrial biosphere reservation area, contains a considerably large area with different types of peat bogs, which were described in three profiles at 1,250, 1,800 and 1,350 m above sea level and classified, respectively, as organosol haplic sapric terric (p1), organosol haplic fibric typical (p2) and organosol haplic hemic typical (p4), in agreement with the brazilian system of soil classification. the three profiles were characterized morphologically and the samples were chemically, physically and microbiologically analyzed. it was found that the location, altitude and drainage influenced the morphologic, physical, chemical, and biological properties of the peat bogs in sdem. the decomposition state of organic matter is more advanced when the drainage in the peat bogs is better. the amount of heavy metals is related with the quantity and granulometric composition of the mineral fraction and location of the peat bogs. the highest mean levels of ti, zr, pb were detected in profile p1, highest mean levels of mn, zn and cu in p2, and the highest mean fe content in p4. the intensity of microbiological activity in the peat bogs p2 and p4 was related with the drainage and heavy-metal content of its layers.
Pedochronology and development of peat bog in the environmental protection area pau-de-fruta - Diamantina, Brazil
Campos, José Ricardo da Rocha;Silva, Alexandre Christófaro;Vasconcellos, Leandro Lara;Silva, Daniel Vallad?o;Rom?o, Rafael Vitor;Silva, Enilson de Barros;Grazziotti, Paulo Henrique;
Revista Brasileira de Ciência do Solo , 2010, DOI: 10.1590/S0100-06832010000600021
Abstract: in the region of the serra do espinha?o meridional, peat bog is formed in hydromorphic environments developed in sunken areas on the plain surfaces with vegetation adapted to hydromorphic conditions, favoring the accumulation and preservation of organic matter. this pedoenvironment is developed on the regionally predominant quartzite rocks. peat bog in the environmental protection area - apa pau-de-fruta, located in the watershed of córrego das pedras, diamantina,brazil, was mapped and three representative profiles were morphologically characterized and sampled for physical, chemical and microbiological analyses. the organic matter was fractionated into fulvic acid (fa), humic acids (ha) and humin (h). two profiles were sampled to determine the radiocarbon age and δ13c. the structural organization of the three profiles is homogeneous. the first two layers consist of fibric, the two subsequent of hemic and the four deepest of sapric peat, showing that organic matter decomposition advances with depth and that the influence of mineral materials in deeper layers is greater. physical properties were homogeneous in the profiles, but varied in the sampled layers. chemical properties were similar in the layers, but the ca content, sum of bases and base saturation differed between profiles. contents of h predominated in the more soluble organic matter fractions and were accumulated at a higher rate in the surface and deeper layers, while ha levels were higher in the intermediate and fa in the deeper layers. microbial activity did not vary among profiles and was highest in the surface layers, decreasing with depth. from the results of radiocarbon dating and isotope analysis, it was inferred that bog formation began about 20 thousand years ago and that the vegetation of the area had not changed significantly since then.
Water retention in a peatland with organic matter in different decomposition stages
Rocha Campos, José Ricardo da;Silva, Alexandre Christófaro;Fernandes, José Sebasti?o Cunha;Ferreira, Mozart Martins;Silva, Daniel Vallad?o;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000400015
Abstract: peatlands are ecosystems formed by successive pedogenetic processes, resulting in progressive accumulation of plant remains in the soil column under conditions that inhibit the activity of most microbial decomposers. in diamantina, state of minas gerais, brazil, a peatland is located at 1366 m asl, in a region with a quartz-rich lithology and characteristic wet grassland vegetation. for this study, the peat area was divided in 12 transects, from which a total of 90 soil samples were collected at a distance of 20 m from each other. the properties rubbed fiber content (rf), bulk density (bd), mineral material (mm), organic matter (om), moisture (moi) and maximum water holding capacity (mwhc) were analyzed in all samples. from three selected profiles of this whole area, samples were collected every 27 cm from the soil surface down to a depth of 216 cm. in these samples, moisture was additionally determined at a pressure of 10 kpa (moi10) or 1500 kpa (moi1500), using richards' extractor and soil organic matter was fractionated by standard procedures. the om decomposition stage of this peat was found to increase with soil depth. moi and mwhc were highest in layers with less advanced stages of om decomposition. the humin levels were highest in layers in earlier stages of om decomposition and with higher levels of water retention at mwhc and moi10. humic acid contents were higher in layers at an intermediate stage of decomposition of organic matter and with lowest levels of water retention at mwhc, moi10 and moi1500.
Microbial and soil properties in restoration areas in the jequitinhonha valley, Minas Gerais
Santos, Danielle Cristina Fonseca;Grazziotti, Paulo Henrique;Silva, Alexandre Christófaro;Trindade, Aldo Vilar;Silva, Enilson de Barros;Costa, Lidiomar Soares da;Costa, Hesmael Ant?nio Orlandi;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000600035
Abstract: to mitigate the impacts of eucalypt monoculture, forestry companies in the upper jequitinhonha valley (mg) have adopted the insertion of strips of native vegetation in-between the commercial plantations. the method used for the creation of these corridors is to allow spontaneous regrowth of native vegetation in areas previously under eucalypt. the objective of this study was to evaluate the effect of cover crops on microbial and soil properties for a detailed description of the restoration process of native vegetation in forest soils of the jequitinhonha valley. the treatments were represented by an initial restoration stage (< 4 years) with or without remaining eucalypt and the advanced restoration stage (> 4 years) with or without remaining eucalypt, plus the three controls: commercial eucalypt plantation, cerrado vegetation and native forest. soil samples were collected for three consecutive years in the dry and rainy season (august and february, respectively). the microbial activity, regardless of the presence of remaining eucalypt , did not differ among the restoration areas, except for the metabolic quotient (qco2) in the rainy season of february 2007. at this time, this microbial activity was higher in the advanced restoration stage without eucalypt than initial restoration without eucalypt and advanced restoration with eucalypt. the restoration areas, in general, did not differ from the control: eucalypt plantation and cerrado either. compared to the forest, the levels of organic c, microbial c, basal respiration (rbasal) and hydrolysis of fluorescein diacetate (fda) in the restoration areas were, in general, lower and did not differ in qco2 and microbial quotient (qmic). in general, the soil quality was similar in the initial and advanced restoration stages. most of the soil and microbial properties in the three years indicated that the restoration areas were most similar to the cerrado. in the advanced restoration areas without eucalypt compared to cerrado
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